The receiver may have 2, 3, 4 or more channels but if you only have a two channel transmitter you would only be able to use the Steering and Throttle (ESC) ports which are typically channel 1 & 2.

In order to use 3, 4 or more you will need a transmitter that offers more channels. These might be used to toggle lights on/off, adjust movable options you have installed, change gears if you have a two speed transmission, etc...